The present invention generally relates to a method and a system for dynamically estimating atmospheric air pressure ambient to an internal combustion engine. The present invention more specifically relates to a control system for executing a method for dynamically estimating atmospheric air pressure ambient to an internal combustion engine in response to various signals relating to the internal combustion engine.
To strive for optimum engine performance, a control system for an internal combustion engine estimates an optimum quantity of fuel injection into a combustion chamber for each combustion cycle of the engine as a function of various operating and environmental conditions of the engine and associated vehicle. Atmospheric air pressure ambient to the internal combustion engine is one of the environmental conditions that must be considered during this process for several reasons. First, the quantity of fuel required to start an internal combustion engine at sea level is significantly higher than the quantity of fuel required to start the engine at high altitudes. Consequently, if the quantity of fuel required to start the internal combustion engine is fixed as a function of atmospheric air pressure at sea level, then fuel is wasted when the engine is started at high altitudes. Conversely, if the quantity of fuel required to start the internal combustion engine is fixed as a function of atmospheric air pressure at high altitudes, then the quantity of starting fuel may be insufficient to start the engine at sea level. Unfortunately, if the quantity of fuel required to start the internal combustion engine is fixed as a function of atmospheric air pressure at an intermediate altitude, then fuel will still be wasted when the engine is started at high altitudes and the quantity of starting fuel may still be insufficient to start the engine when the engine is at sea level. In addition, the internal combustion engine will experience excessive black smoke while operating at low boost levels when the engine is at high altitudes.
Second, aggressive fuel timing advances for the internal combustion engine are required to control white smoke levels from the engine when the engine is at high altitudes. However, if aggressive fuel timing advances are implemented at all altitudes, the internal combustion engine will experience significantly high levels of noise when the engine is at sea level. Finally, there is also the need to derate the fuel parameters of the internal combustion engine when the engine is at high altitudes to protect engine components from significant wear and tear. Consequently, if the fuel parameters of the internal combustion engine are fixed as a function of atmospheric air pressure at sea level or an intermediate altitude, then the repair and maintenance cost of an internal combustion engine predominately at high altitudes will significantly exceed the repair and maintenance cost of an internal combustion engine predominately at sea level.
A solution known in the art for dynamically determining atmospheric air pressure ambient to an internal combustion engine is the addition of an atmospheric air pressure sensor positioned within a passenger compartment of a vehicle. An electronic control unit receives a signal from the atmospheric air pressure sensor and determines the proper amount of fuel injection into a combustion chamber for each combustion cycle of the engine as a function of the atmospheric air pressure signal. A problem associated with this solution is the added expense of having an additional sensor and the associated wiring as well as any additional repair and/or replacement costs attributed to the atmospheric air pressure sensor. Another problem is the requirement for an additional input signal path to the electronic control unit that decreases the reliability of the electronic control unit by increasing the number of potential failure points leading to the electronic control unit. Thus, the cost of monitoring and testing the atmospheric air pressure sensor and the associated input signal path is also incurred.
A solution known in the art for estimating atmospheric air pressure ambient to an internal combustion engine is the utilization of a signal from a boost sensor positioned within a suction pipe of the engine to detect the pressure downstream from a throttle valve also positioned within the suction pipe. The boost sensor signal is sinusoidal due to the cyclical opening and closing of the throttle valve. Atmospheric air pressure ambient to the engine is estimated as a function of the maximum ripple value of the boost sensor signal immediately after the engine is started. However, this estimation method is not dynamic since it is not executed when the engine is running. Alternatively, atmospheric air pressure ambient to the engine is estimated as a function of the average value of the boost sensor signal as the engine is running. However, this estimation method is not dynamic since it is not executed at least once for each combustion cycle of the internal combustion engine.
In view of the foregoing issues, there is a need for dynamically estimating atmospheric air pressure ambient to an internal combustion engine. The present invention satisfies these needs in a novel and unobvious manner.
The foregoing shortcomings of the prior art are addressed by the present invention. In one aspect of the present invention, a method for estimating atmospheric air pressure ambient to an internal combustion engine comprises a first step of estimating the atmospheric air pressure as a function of the absolute boost pressure of the internal combustion engine when the internal combustion engine is idling, and a second step of estimating the atmospheric air pressure as a function of both the absolute boost pressure and the engine speed of the internal combustion engine when the internal combustion engine is running in a steady state.
In a second aspect of the present invention, a system for estimating atmospheric air pressure ambient to an internal combustion engine comprises a means for estimating the atmospheric air pressure as a function of the absolute boost pressure of the internal combustion engine when the internal combustion engine is idling, and a means for estimating the atmospheric air pressure as a function of both the absolute boost pressure and the engine speed of the internal combustion engine when the internal combustion engine is running in a steady state.
One object of the present invention is to provide a method for dynamically estimating atmospheric air pressure ambient to an internal combustion engine.
Another object of the present invention is to provide a system for executing a method for dynamically estimating atmospheric air pressure ambient to an internal combustion engine.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.